1. Field of the Invention
The present invention generally relates to an electronic still camera and, more particularly, relates to an electronic still camera for converting and recording a still image signal into a plurality of streams.
2. Description of the Related Art
A conventional electronic still camera converts an optical image projected by a lens 2 using a solid-state image pick-up element 1 such as a CCD (charged-coupled device) into an electrical signal, as shown in FIG. 5. This signal is subjected to desired processing by, e.g., an amplifier 3, a process circuit 4, and the like, and the processed signal is then recorded in a signal recording device 5 as a recording device. The signal recording device 5 comprises a recording medium such as a magnetic disk, an IC memory, or the like, and the above-mentioned signal is recorded on this recording medium.
In particular, when the recording medium is assumed to be a solid-state memory element such as an IC memory or a ferroelectric memory, the obtained video signal is converted to a digital signal by an A/D converter 6, and the digital signal is then recorded by the signal recording device 5. The signal recording device 5 is detachable with respect to an image pick-up unit 7 of an electronic still camera.
As the solid-state memory element used in the signal recording device 5 of the electronic still camera, a static random-access memory (SRAM), an electrically erasable programmable read-only memory (EEPROM), or the like is used. In particular, since the EEPROM is of a nonvolatile type, long-term recording can be attained without using a backup power source in the signal recording device 5.
However, the write speed of the EEPROM is as low as 1 ms/bit. For this reason, when the EEPROM is used in the electronic still camera to record a still video signal, about several hundreds of seconds are required to record a still image of one frame (about 2 Mbits) even if signal compression processing by, e.g., encoding is executed. Therefore, when the EEPROM is used as the recording medium of the signal recording device of the electronic still camera, a considerable wait time is required after a certain photographing operation until the next photographing operation can be started, and, hence, a continuous photography mode for performing continuous photographing operations cannot be realized.
For this reason, as disclosed in U.S. Pat. No. 4,803,554, a high-speed buffer memory such as a dynamic random-access memory (DRAM) may be arranged in the electronic still camera to realize continuous photographing operations. However, in this case, a buffer memory having a considerably large capacity is required, and a circuit scale is increased, resulting in high cost of the overall apparatus.